Start-stop telegraph signal generator



1 1959 J. GARDBERG 2,900,448

START-STOP TELEGRAPH SIGNAL GENERATOR Filed Nov. 14, 1955 3 Sheets-Sheet 1 INVENTOR FIG. I JOSEPH GARDBERG ATTORNEY Aug. 18, 1959 J. GARDBERG START-STOP TELEGRAPH SIGNAL GENERATOR Filed Nov. 14, 1955 I 3 Sheets-Sheet 2 I i INVENTOR JOSEPH GARDBERG ATTORNEY FIG. 2

Aug. 18, 1959 J. GARDBERG 2,900,448

START-STOP TELEGRAPH SIGNAL GENERATOR Filed Nov. 14, 1955 3 Sheets-Sheet 3 l l I v ,I I

I i t l 9 g E, w l m O 2 u) "0 E :1 E O 29 a: n. 9 2 on: 0 on: 00 m we INVENTOR FIG.3

ATTORNEY JOSEPH GARDBERG v 1 Another object United States Patent START-STOP TELEGRATH SIGNAL GENERATOR Joseph Gardberg, Chicago, Ill., assignor to Teletype Corporation, Chicago, 111., a corporation of Delaware Application November 14, 1955, Serial No. 546,385

6 Claims. c1. 178--26) This invention pertains to a generator for producing start-stop telegraph signals and more particularly to apparatus for generating from a multi-wire source of permutation signal impulses, a start-stop signal and applying said signal to a single transmission line.

In the transmission of telegraph signals from one locationito another it is usually desirable to use start-stop signals, but often the source of signals is a punched tape or other storage medium which does not store the start and stop impulsesthat are to accompany each transmitted signal. Inasmuch as the start and stop impulses are of fixed characteristic for each signal, local devices have been devised for automatically adding the desired start and stop impulses. Heretofore, both mechanical and electronic devices have been provided to add the start and stop impulses. In general these prior devices have proved satisfactory but the mechanical devices possess an inherent disadvantage in that they are limited as to the speed at which perfect signals can be generated. Though the-previous electronic devices have operated at adequate speeds, the devices have in general depended upon a distributor driven by an oscillator that must be started and stoppedduring each cycle of. operation. Where. continuously, running oscillators have been employed it has not been feasible to .generateastop impulse having a duration other than the .length ofthe start and intelligence impulses. In present day start-stop transmission systems it ,isidesirable to have the length of the stop impulse be 1.42 times -the.length of the start and intelligence impulses. This limitation of .s-constant running oscillator [transmitters is due to the fact that the known oscillators produce outputs at a constant frequency.

fit is a primary object of thepresent invention to provide an oscillator-thatlproduces a predetermined number of'outputs at a constant predetermined frequency and "then'prod-uces the next output at a different predeterimin df eq n ya Concomitant with the first object, it is a further object to provide an oscillator having a variable frequency output that iscontrolled by a distributor driven by the oscillator; I of the invention is to provide a phantastron oscillator in combination with a control cir- 'ci it whereby the linear drop of anode potential may be iedito accordingly vary the outputof the oscillator.

'1 Another object of the invention resides in the combinationof an oscillator. with a start-stop multi-stage tele- "graph transmitting distributor wherein the oscillator con tinuously drives the transmitting distributor to generate n stageiof the distributor actuates a control circuit for changing the frequency of the oscillator.

,s with these andotherobjects in view the present invention contemplates a phantastron oscillator adapted to 2,900,448 Patented Aug. 18, 1 959 ice drive a start-stop multi-stage distributor through successive cycles of operation. The output of the distributor is combined in a gating circuit with signal impulses from .a signal storage medium to produce start-stop telegraph signals.

The phantastron oscillator has a period of oscillation which is determined by the time that its anode potential drops to a minimum value. The shape of the drop in anode potential is controlled by a resistive capacitive cir cuit coupled to a source of positive potential. As the last stage of the distributor is actuated, a control circuit is operated to change the potential applied to the resistive capacitor network associated with the phantastron and consequently the period of oscillation of the phantastron is changed. This change is in the nature of a prolongation of the time required for the anode potential to reach its minimum value. As a consequence of the delayed action of the phantastron, the stop stage of the distributor is held operated for a prolonged period of time and this time is represented by the time required to generate a stop 'nnpulse which .may be utilized in all standard telegraph repeating, switching and receiving equipments.

Other objects and advantages of the present invention will be apparent from the following detailed description when considered in conjunction with the accompanying drawings wherein:

Figs. 1 and 2, when assembled in the manner instructed by Fig. 3, show a schematic circuit diagram illustrating a signal generator embodying the principal features of the present invention; and

Fig. 4 is a wave form diagram showing the various potential conditions on various electrodes in a phantastron oscillator.

Referring to Figs. 1 and 2 when assembled in the manner taught in Fig. 3, there is shown in the lower righthand corner a source of signals within the dashed line box 10. This instant source of signals comprises a binary circuit which is adapted to generate signals in accordance with the Baudot code representative of the letters R and Y. The output from the source of signals is impressed over leads 11 to 15 to diode gating circuits represented by the reference numerals 17, 18, 19, 20 and 21. .Positioned above the gating circuits and adapted to feed conditioning potential to the gating circuits is, a multi-stage distributor within the dashed line box 22. The distributor is adapted to be driven through its various stages by an oscillator contained in the dashed line box 24. As the oscillator produces driving pulses, 'tubes 26, 27, 28, 29, 30, 31 and 32 are successively operated. When the first tube 26 is operated, an output transmission lead 34 is not connected thereto and as a result has no potential applied thereon. This condition is representative of a start impulse condition.

As each succeeding tube 27 through 31 is operated conditioning potentials are applied to the respective gating circuits 17, 18, 19, 2t and 21. If a gating circuit has a potential condition applied thereto from the source of signals 10, then an output potential is impressed on the lead 34 which is representative of a marking signal impulse. If there is no potential condition impressed on the gating circuit from the source 10, then the operation of the tube is ineffective to cause the operation of the gating circuit, and as a result thereof a spacing condition is impressed on the output lead 34. v

It will be noted that a gate 33 associated with the tube 32 is permanently connected to the output lead 34 and to a source of positive potential; hence, upon tube 32 operating, a potential or marking condition is impressed on the lead 34 which condition is indicative of a stop impulse. When the stop tube 32 operates, an amplifier tube 36 is also operated. Operation of this tube is follower by a drop in its anode potential which drop is impressed on a lead 37 to the oscillator. The decrease 3 in potential on the lead 37 prolongs the period of operation of the oscillator, hence, holding the tube 32 in an operative condition for a greater period of time than the other distributor tubes. The drop in potential on 'lead 37 is selected so that the stop tube is held energized for a period of time which is 1.42 times the length that any of the other distributor tubes are operated.

When the oscillator 24 generates the next pulse to render the tube 32 nonconductive, the tube 26 is again rendered conductive to initiate a new cycle of operation of the transmitting distributor. When the stop tube 32 was operated, a pulse of increased potential was applied over a lead 38 to operate the signal source to change utilized to step the tape along one increment to present a new transverse row of permutations of holes to the reading elements which would thereupon impress a new permutation of potential conditions on the leads 11 to 15.

Considering each one of the units in detail, the oscillator 24 is a screen coupled phantastron with a cathode follower tube 41 to speed recovery of the timing circuit controlling the period of oscillation of the phantastron. More particularly, the oscillator comprises a pentode 42 having an anode 43, a suppressor grid 44, a

screen grid 46, a control grid 47 and a cathode 48. The suppressor grid 44 and screen grid 46 are respectively connected through resistances 49 and 51 to positive .battery and further are coupled to each other through a condenser 52. This coupling condenser insures that the suppressor grid will vary in direct proportion to variations in potential on the screen. Anode 43 is coupled to the control grid 47 through the tube 41 and a condenser 53.

With battery connected as shown, wave forms for the various oscillatorcomponents such as shown in Fig. 4 will be obtained. Considering the condition of the oscillator at state A which is only of instant duration, the potential of the anode 43 has run down to its lower limit as determined by the space charge in the tube 42. Inasmuch as the anode 43 can no longer drop and thus supply negative charges to the left-hand plate of the condenser 53, the control grid 47 is no longer held negative. Now the potential of the control grid is deter- 'mined by a circuit connected to positive battery which may be traced through a resistance 57, an adjustable re sistance 58, an adjustable tapped resistance 59. and a .resistance 60 connected to a source of positive potential The control grid 47 rises to a slightly positive value and as a result the screen grid 46 is permitted to draw heavy current thereby causing its potential to rapidly drop. Since the suppressor grid 44 is coupled by the condenser 52 to the screen grid 46, the suppressor grid potential also rapidly drops to preclude any further flow of anode current. Immediately thereupon, the potential of anode 43 rises to cause a rise in the potential applied to the grid of tube 41 and as a result thereof this tube is driven into a heavy state of conduction causing its cathode potential to rise. As the cathode potential of the tube 41 rises, a positive charge is placed on the lefthand plate of the condenser 53 due to the charging circuit running from cathode 48 and grid 47 through the condenser and now conducting tube 41.

As previously mentioned, the screen grid 46 draws heavy current and its potential drops very rapidly to drive the suppressor grid 44 negative, but this action can only continue until the potential drops to a value determined vby the values of the resistance 49 and the potential source connected thereto. When the lower limit of drop in screen grid potential is reached, the coupling condenser 52 commences to discharge through resistance 51 to the source of positive potential. At this time, the suppressor grid 44 can no longer obtain negative charges from the condenser 52 and since this suppressor grid is connected through resistance 49 to positive battery, its potential will immediately rise very rapidly. As the potential on the suppressor approaches ground or zero potential the anode 43 will again be permitted to conduct.

Conduction of current through the anode 43 is accompanied by an immediate drop in potential which drop is applied to the grid of tube 41 driving this tube toward a nonconductive state. As tube 41 is driven toward nonconduction, its cathode potential drops to impress negative charges through condenser 53 to drive the control grid negative. When the control grid 47 is driven sufficiently negative, it regains control of the current flow through the tube 42 to reduce the current flowing to the screen grid 46 and as a result the screen grid potential rapidly rises.

Following the immediate drop in potential of the anode 43, the anode Will continue to drop at a rate suflicient to hold the control grid 47 at a negative value whereby the control grid 47 continues to keep the screen current flow at a minimum. The drop in anode potential is a linear run down which is a function of the discharge circuit associated with condenser 53. The rate of discharge of this circuit is a function of the values of the capacitance 53, the resistance 57, the adjustable resistance 58, the tapped resistance 59, the resistance 60 and the source of potential 61.

If any of these elements is varied, the effect is to vary the duration of the period of run down of anode potential. More particularly, if the source of potential 61 is lowered in value, then the rate of discharge of the condenser 53 is decreased and as a result there is an increase in the time of the run down of the potential of the anode 43. This result is apparent when it is recalled that the positive potential source 61 is counteracting the effect of the decreasing anode potential and thus with a lower source of potential 61, the anode need only drop at a slower rate to supply the necessary negative charges to hold the control grid 47 at the negative potential.

The frequency'of the oscillator may be varied by limiting the positive excursion of the anode potential. In the illustrated oscillator the anode 43 is connected through a diode 64 to a tap on an adjustable resistance 66 which is connected to the source of positive potential. If the tap is moved downwardly to increase the resistance of the anode circuit, the maximum anode potential attainable is likewise decreased and as a result the linear run down of the anode potential will be curtailed. Dotted line a in Fig. 4 illustrates an example of a starting point for a decreased period of run down of the anode potential. It may be readily observed that the run down will now occur in a much shorter time interval and manifestly the frequency of the oscillator increases.

In addition the frequency of the oscillator may be varied by changing the slope of the run down of the anode potential. It is to be recalled that the slope of the run down anode potential is determined by the rate of the discharge of the condenser 53 through the resistive circuit including the resistances 57, 58, 59 and 60. This discharge circuit provides for a fairly rapid rate of discharge due to the potential gradient between the source of positive potential 61 and the negative charge on the condenser 53.

The source of positive potential 61 is also connected through a resistance 68 to the anode of the tube 36. This tube is of a vacuum type and is normally nonconductive therefore it does not influence the potential gradient between the tap on the resistance 59 and the condenser 53. However, if this tube 36 is rendered conductive then its anode potential drops and the potential at the tap of the adjustable resistance 59 also drops.

In this instance the potential gradient betwen the tap on the'resistance' 59 and the negatively charged condenser 53 drops to thereby slow down the rateat which the condenser is discharged through the resistance network. With a slowing down of the rate of discharge, the slope of the run down in anode potential is also decreased, consequently the period of oscillation of the tube is prolonged. An example of such a prolongation in the period of oscillation of the tube 42 is shown in Fig. 4 and is denoted therein by the reference letter B.

' With the operation of the oscillator in mind, a detailed description of the operation of the signal generator may be readily understood. Assume that battery has just been applied to the apparatus and that a tube 71 in the signal source 19 has fired. Then, its cathode potential rises'to impress an increased potential over leads 11, 13 and 15. Looking at the distributor 22, it consists of a plurality of cathode coupled gaseous discharge tubes 26 to 32. These tubes each possess the characteristic that once rendered conductive the tube will remain in such 'a state independently of the potential applied to its con- ;trol grids. The only way that conduction can be terminated is to either raise the cathode potential or lower the anode potential to such an extent that the potential gradient across the tube is insufficient to maintain the flow of current therethrough. It will be further noted that each of the anodes of the tubes are connected through a common resistance 72 to the source of positive potential 61 and the cathodes of the tubes are connected to resistance-capacitance circuits; thus, an arrangement of tubes is provided whereby only one can sustain conduction at anyone time. I

x'When power is applied to the distributor the anode potentials of all tubes are raised but inasmuch as the anode of the tube 32 is coupled through a resistance 73 to its control grid this tube will immediately fire. The

circuitry of tube 32 is such as to cause its cathode potential to rise to impress an increased potential through a diode gate 33 connected to the output line 34. This potential condition is indicative of a marking condition. The rise in cathode potential of this tube is also impressed over the lead 33, through a coupling condenser to a junction point between the tube 71 and a tube 76. The appearance of an increased potential at this junction point will render the nonconductive tube conductive whereupon its anode potential will drop. The drop in anode potential causes the conductive tube to be rendered nonconducting due to the capacitance network connected in the cathode circuit of each tube. More specifically, assume that tube 76 was conducting, then the appearance of an increased potential at junction point between the tubes causes the tube 71 to commence conduction. Inasmuch as there is a capacitance network connected in the cathode circuit of the tube 71, the cathode potential will be precluded from rapidly rising. It will be also noted that a capacitance network is connected to the cathode of the conducting tube 76, thereby holding the cathode of this tube at a relatively high potential. Thus, when the tube 71 commences to conduct and the anode potential of both tubes drop, then the potential gradient within the tube 76 will be insufiicient to maintain conduction and hence only the tube 71 will be maintained in the conductive state.

When the tube 32 is operated, the rise in its cathode potential is also impressed over a lead 77 to the grid of the amplifier tube 36. As previously discussed, when the tube 36 is rendered conductive, the potential at the tap on resistance 59 is decreased, hence the available positive potential to discharge the capacitor 53 (see oscillator 24) is reduced; consequently, the oscillator 24 will execute a prolonged cycle of operation. Following a cycle of operation of the oscillator the screen grid 46 drops in potential. This drop in potential is impressed through a condenser 79 to the grid of an amplifier tube 81. The amplifier tube 81 is normally conductive due to the positive potential applied to its grid which potential is determined by a voltage divider consisting of resistances 83 and 84. When the negative impulse appears on the grid of the tube 81, it will be momentarily rendered nonconductive causing its anode potential to rise.

During the instant that the tube 81 is shut ofi, a positive pulse is impressed over a lead 86 to the control grids of all the tubes 26 to 32. It will be noted that these tubes have capacitance networks included in their cathode circuits and further that each cathode is coupled to a control grid of the next succeeding tube in the distributor. Considering tube 32, it will be noted that the cathode is coupled by a lead 87 to a control grid 89 of tube 26. Inasmuch as tube 32 is in a conductive state then an increased potential will be applied on the grid 89 to condition the tube 26 for operation. The positive pulse from the oscillator impressed on lead 86 further raises the potential of the grid 89 to render the tube 26 conductive. When tube 26 conducts its anode potential immediately drops and inasmuch as the anode of tube 32 is coupled thereto the anode potential of tube 32 will likewise drop. Recalling that capacitance circuits are connected in the cathode circuits of both tubes 26 and 32 then it will be understood that the potential gradient in tube 26 will be much larger than that existing in tube 32. In fact the potential gradient in tube 32 will be decreased by such an amount as to render this tube nonconductive.

When the tube 32 is rendered nonconductive, then the amplifier 36 is shut oil and, as a result, potential on the tap of the resistance 59 again rises to its normal value and thereafter the oscillator 24 will produce positive pulses at the regular frequency.

It will be noted that the cathode of the tube 26 is not connected to the lead 34 and as a result when the tube 26 is rendered conductive there will be no potential impressed on the output lead34. This condition is indicative of a start impulse. The succeeding positive pulses impressed over lead '86 from the oscillator 24successively operate the tubes 27, 28, 29, 30 and 31. Recalling that the leads 11, 13 and 15 have potential applied thereto then it may be appreciated that as the tubes are successively operated, the gates 17, 19 and 21 will be successively operated to impress a potential or marking condition on the output lead 34. In a like manner, when the tube '76 in the signal generator 10 is operated, the tubes 28 and 30 in conjunction with the potentials applied .on the leads 12 and 14 will operate the gates 18 and 20 to impress marking conditions on the output line. The circuit will now continue to function generating startstop RY signals wherein each stop impulse will be of a longer duration than any of the other impulses.

It is to be understood that the above-described arrangeof circuits and construction of elemental parts are simply illustrative of an application of the principles of the invention and many other modifications and changes may be made without departing from the invention.

What is claimed is:

1. An electronic distributor comprising a plurality of electronic stages, an oscillator for driving the electronic stages through a cycle of operation, means for controlling the oscillator to operate at a predetermined frequency, and means actuated by one of said electronic stages for imparting to at least one stage of said distributor an operative interval difierent from that of at least one other stage by changing the frequency of operation of said oscillator.

2. In a transmitting distributor, a plurality of electronic tubes coupled together so that only one can maintain operation at one time, an oscillator for successively operating the tubes, timing means within the oscillator for controlling the oscillator to operate at a predetermined frequency, and means operated by one of said tubes for imparting to said one tube an interval of operation different from that of all others of said tubes by changing the effect of the timing means to cause the oscillator to .change its frequency of operation.

3. In a start-stop signal generator, a source of intelligence signals, an electronic multi-stage distributor means for combining the output of said source of signals and a predetermined number of said distributor stages to generate an intelligence portion of a start-stop signal, a start stage included in said distributor for controlling the generation of a start impulse to precede the intelligence portion of the start-stop signal, a stop stage included in said distributor for controlling the generation of a stop impulse to follow the intelligence portion of the start-stop signal, an oscillator for continuously driving said distributor, and means controlled by the stop stage of the distributor for prolonging the period of operation of said oscillator to efiectuate the generation of a stop impulse .which is longer than the other impulses of the start-stop signal.

4. In a code converter for applying signals from a multi-wire source to a single transmission line, a multistage distributor having an electron discharge tube in each stage, said tubes being intercoupled in a closed ring to cause each tube When conductive to prepare the next tube in the ring for conductivity, gating circuits interconnecting the multi-wire signal source and the stages of the distributor to the single transmission line, an oscillator for driving the distributor to cause each tube to conduct successively for an interval equal to one cycle of said oscillator whereby the gating circuits are operated in ac cordance with signal conditions in the multi-wire signal source, a potential source for controlling the period of oscillation of the oscillator, and means actuated by the operation of one stage of the distributor for changing the effective value of the potential source to vary the period .of oscillation of the oscillator and accordingly the duration of at least one cycle thereof.

5. In start-stop signal generator, a source of simultaneous signal elements, a distributor having a plurality of stages corresponding to each signal element, a stage for generating a start impulse, a stage for generating a stop impulse, a constantly running oscillator having a delay circuit for generating stepping pulses for said distributor at a predetermined uniform frequency, means for applying each generated pulse to all the distributor stages to successively operate each stage of the distributor, means to combine the output of each stage and the signal elements to produce a continuous series of signal elements, and means operated by the stop stage for changing the period of operation of the delay circuit to cause the oscillator to postpone for a predetermined period of time the production of the next stepping pulse.

6. In an electronic distributor having an electronic valve in each stage, means intercoupling said valves in a closed ring to cause each valve, when conductive, to prepare the next valve in the ring for conductivity, an oscillator, means coupling said oscillator to said valves to cause each valve to conduct for an interval equal to one cycle of said oscillator, and means controlled by one of said valves for changing the frequency of said oscillator to accordingly change the duration of a cycle thereof and the duration of conductivity of the valve causing said change.

References Cited in the file of this patent UNITED STATES PATENTS 2,283,919 Diamond May 26, 1942 2,287,786 Diamond June 30, 1942 2,462,134 Scully Feb. 22, 1949 2,521,353 Fitch Sept. 5, 1950 2,616,047 Boothroyd Oct. 28, 1952 2,662,114 Beard Dec. 8, 1953 OTHER REFERENCES Radiation Laboratory Series, vol. 19, entitled Waveforms, page 197. 

